Add my answer to Exercise 3.12.

Included are the following 3 files:

	Exercise_3.12.pdf
	Exercise_3.12.scm
	Exercise_3.12.tm

Thank you!
							Lawrence X. Amlord
							  Sept 21st, 2013
							  Xi'an, China
Add my answer to Exercise 3.13.

Included are the following 3 files:

	Exercise_3.13.pdf
	Exercise_3.13.scm
	Exercise_3.13.tm

Thank you!
							Lawrence X. Amlord
							  Sept 21st, 2013
							  Xi'an, China
Add my answer to Exercise 3.14.

Included are the following 3 files:

	Exercise_3.14.pdf
	Exercise_3.14.scm
	Exercise_3.14.tm

Thank you!
							Lawrence X. Amlord
							  Sept 21st, 2013
							  Xi'an, China